The present invention relates to a control type booster having an automatic brake function, which electromagnetically operates an atmospheric air valve or a vacuum valve.
As an example of a control booster of the above-mentioned type, there can be mentioned a control booster comprising: a power piston dividing the inside of a housing into a constant pressure chamber and a variable pressure chamber; a valve mechanism adapted to control the supply of a working fluid to the variable pressure chamber, in accordance with movement of a plunger connected to an input rod associated with a brake pedal, the valve mechanism being provided in a valve body supported by the power piston; an electromagnetic bias means having a movable element which operates the valve mechanism independently of operation of the input rod; an electromagnetic solenoid connected to a power source and adapted to receive electric power and move the plunger; and a switch connected to the power piston and provided in the constant pressure chamber. The control booster further comprises a switch rod axially movable together with the input rod. The switch rod operates the switch when the input rod moves a predetermined distance relative to the power piston.
In this control booster, a braking force is generated by utilizing a differential pressure between the variable pressure chamber and the constant pressure chamber, which is generated by operation of the brake pedal (braking effected in this manner is hereinafter referred to as xe2x80x9cthe pedal-operated brake operationxe2x80x9d for convenience""s sake). Further, the control booster is capable of generating a braking force by generating a differential pressure between the variable pressure chamber and the constant pressure chamber due to operation of the electromagnetic bias means, independently of operation of the brake pedal (and hence the input rod) (braking effected in this manner is hereinafter referred to as xe2x80x9cthe automatic brake operationxe2x80x9d for convenience""s sake).
In the above-mentioned control booster of the related art, since the switch rod is connected to or engaged with the plunger, the amount of movement of the plunger is directly transmitted to the switch (a stationary contact of the switch) and the switch is operated by undesirably large force, leading to breakage of the switch.
Further, in the control booster, for effecting the pedal-operated brake operation during the automatic brake operation, it is desired to discontinue the automatic brake operation. To this end, it is considered to utilize the switch of the above-mentioned related art for detecting the pedal-operated brake operation during the automatic brake operation. However, in the switch of the above-mentioned related art, as mentioned above, the amount of relative movement of the plunger is directly transmitted to the switch, so that breakage of the switch is likely to occur. In fact, it is difficult to utilize the switch of the above-mentioned related art so as to discontinue the automatic brake operation for effecting the pedal-operated brake operation in an appropriate manner.
Further, as another example of the related art, there is a control booster described in Japanese National Publication (Kohyo) No. 10-505041 of PCT Application. In this control booster, the switch is provided in the variable pressure chamber. Therefore, the control booster encounters a problem that the switch is subject to atmospheric pressure each time the brake pedal is operated, so that the pressure applied to the switch frequently changes.
In view of the above situation, the present invention has been made. It is an object of the present invention to provide a control booster capable of appropriately detecting the pedal-operated brake operation during the automatic brake operation.
It is another object of the present invention to reduce a change in pressure acting on the switch.
The present invention provides a control booster comprising:
a power piston dividing an inside of a housing into a constant pressure chamber and a variable pressure chamber;
a valve mechanism which controls supply of a working fluid to the variable pressure chamber in accordance with movement of a plunger connected to an input rod associated with a brake pedal, the valve mechanism being provided in a valve body supported by the power piston;
an electromagnetic bias means having a movable element which operates the valve mechanism independently of operation of the input rod, the control booster being adapted to generate a thrust in the power piston due to a differential pressure generated between the variable pressure chamber and the constant pressure chamber based on operation of the valve mechanism;
a switch for detecting relative movement of the input rod relative to the valve body;
a switch operating rod for operating the switch; and
a switch spring for biasing the switch operating rod in a direction for pushing-in a contact operating element of the switch,
wherein when the input rod is operated in a direction for increasing an output of the booster in a state where a reaction force of the switch acting on the switch operating rod and a spring force of the switch spring are balanced, the switch operating rod moves in a direction for separation relative to the switch.
The present invention also provides a control booster comprising:
a power piston dividing an inside of a housing into a constant pressure chamber and a variable pressure chamber;
a valve mechanism which controls supply of a working fluid to the variable pressure chamber in accordance with movement of a plunger connected to an input rod associated with a brake pedal, the valve mechanism being provided in a valve body supported by the power piston;
an electromagnetic bias means having a movable element which operates the valve mechanism independently of operation of the input rod, the control booster being adapted to generate a thrust in the power piston due to a differential pressure generated between the variable pressure chamber and the constant pressure chamber based on operation of the valve mechanism;
a switch for detecting relative movement of the input rod relative to the valve body;
a switch operating rod for operating the switch; and
a switch spring for biasing the switch operating rod in a direction for pushing-in a contact operating element of the switch,
wherein in a brake pedal non-operated state in an automatic brake mode, the switch operating rod is pressed by the valve body through a pivot lever pivotably supported on the plunger and is separated from the switch and wherein when the input rod is operated in a direction for increasing an output of the booster in the brake pedal non-operated state in the automatic brake mode, the switch operating rod is freed from a pressure of the valve body applied through the pivot lever and abuts against the switch.
The present invention further provides a control booster comprising:
a power piston dividing an inside of a housing into a constant pressure chamber and a variable pressure chamber;
a valve mechanism which controls supply of a working fluid to the variable pressure chamber in accordance with movement of a plunger connected to an input rod associated with a brake pedal, the valve mechanism being provided in a valve body supported by the power piston;
an electromagnetic bias means having a movable element which operates the valve mechanism independently of operation of the input rod, the control booster being adapted to generate a thrust in the power piston due to a differential pressure generated between the variable pressure chamber and the constant pressure chamber based on operation of the valve mechanism;
a switch for detecting relative movement of the input rod relative to the valve body;
a switch operating rod for operating the switch;
a switch spring for biasing the switch operating rod in a direction for pushing-in a contact operating element of the switch; and
an operating member for pressing the switch operating rod against an action of the switch spring and moving the switch operating rod in a direction for separation relative to the switch.